[improve-str-split] add split by spaces (#783)

Author: sk1418

core-kotlin-modules/core-kotlin-strings/src/test/kotlin/com/baeldung/split/StringSplitUnitTest.kt

@@ -57,6 +57,18 @@ class StringSplitUnitTest {
         assertThat(info.split(pattern, 3)).containsExactly("28", "32", "2 / 64 = 29")
     }
 
+    @Test
+    fun `when split by regex, should use regex object instead of string regex`() {
+        val info = "a b    c      d"
+
+        //split by literal regex string won't work in Kotlin:
+        assertThat(info.split("\\s+")).containsExactly(info)
+
+        // a Regex object is required:
+        assertThat(info.split(Regex("\\s+"))).containsExactly("a", "b", "c", "d")
+        assertThat(info.split("\\s+".toRegex())).containsExactly("a", "b", "c", "d")
+    }
+
     @Test
     fun `splitToSequence works lazily`() {
         val info = "random_text,".repeat(1000)
@@ -89,4 +101,4 @@ class StringSplitUnitTest {
         assertEquals("grapes", fruitsArray[2])
         assertEquals("orange", fruitsArray[3])
     }
-}
+}